I have a pair of 40mm Terra Speeds that I bought new for this season, but ended up getting a new gravel bike that came with Goodyear Connector 40mm tires setup tubeless. The Connectors are pretty comparable and I’ve been happy with them so far, so I’m selling the Terra Speeds.
1/ Anecdotally, I found that the Connectors were about as fast as the Terra Speeds on loose gravel. I also found they handled very nicely. However, they lose on rolling resistance as soon as you hit smooth gravel or tarmac.
2/ bicyclerollingresistance.com measures Crr (hence Watts) on a smooth drum which emulates smooth pavement. To get the total Crr you multiply x2 since they give the number per tire.
Using an intermediate power number of 200W:
Connector: Crr 0.01882 @ 200W = 26.9 kph
Terra Speed: Crr 0.01248 @ 200W = 29.9 kph
Using a rec power number of 140W:
Connector: Crr 0.01882 @ 140W = 21.9 kph
Terra Speed: Crr 0.01248 @ 140W = 25.1 kph
Almost counterintuitively, you can see that rolling resistance actually plays a bigger factor at lower powers due to the lower speed and less aerodynamic drag.
I’ll be doing a 2nd gravel TT on the Terra Speeds soon, and I’ll be able to compare the data to how the Connectors performed the first time around in real life
In real life, I don’t think the difference is as big as this especially as the surface gets rougher, but it is definitely going to cost some speed.
…one more thing. 40mm tires might actually have lower rolling resistance than the 35mm versions. They take an aerodynamic and weight hit however, negating the effect.
True . I wouldn’t worry too much about it. Any loose gravel and it’s pretty even. I honestly didn’t find them that slow, except when I was considering asphalt or super smooth gravel. Conversely I thought they cornered better than the TS.
Keep in mind the Terra Speeds are pretty much the fastest gravel tires. Other tires on the market are closer to the Connectors.